[46.09] Unusual Lightcurves in the Vesta Family of Asteroids

A photometric survey of the Vesta family of asteroids was
undertaken by the authors (beginning in 1999) in an effort
to better understand the outcomes of large-scale collisions
in the solar system. Although most of the objects studied
have displayed the usual doubly periodic curves associated
with tri-axial ellipsoids, a few have revealed more unusual
features. Observations from 2002, 2003, and 2004 of 3782
Celle displayed anomalous attenuations superimposed on a
doubly periodic lightcurve. This result for Celle has been
interpreted (Ryan et al. 2003) to represent an asynchronous
binary system where the primary is rotating with a 3.87 hour
period and the secondary is orbiting with a 36.6 hour
period. 3703 Volkonskaya has also displayed a similar
lightcurve signature in data obtained in 2000 and 2003 with
anomalous attenuations occurring with a periodicity of ~24
hours superimposed on a doubly periodic 3.24 hour structure.
However, insufficient data exists to determine whether this
24-hour periodicity is an alias or not. In 2000, 3155 Lee
displayed a lightcurve period of 8.31 hours, but with 4
maxima and minima per cycle. Since these variations are
grouped in pairs with significantly different amplitudes, it
is tempting to also interpret this as a doubly periodic
lightcurve with superimposed anomalous attenuations due to
the presence of a small satellite. However, since the
orbital period would be synchronous with the primary's
rotational period, it would be difficult to distinguish this
effect from one due to surface features. Since the Vesta
family is believed to have been created via a cratering
event, analysis of these of unusual objects has important
implications for understanding possible ejecta
reaccumulation and satellite formation in subcatastrophic
collisions.

This work is supported by the NASA Planetary Astronomy
Program and the generous observing time made available by
the Vatican Observatory Research Group and NOAO.